1. Field of the Invention
The present invention relates to an elastic product provided with a substrate which comprises at least rubber or elastomer.
2. Description of the Related Art
First Prior Art
Conventionally, a master brake cylinder for vehicles, serving to convert the force applied to a brake pedal into a hydraulic pressure, comprises a reservoir for storing the brake fluid and a cylinder for generating the hydraulic pressure. Generally, a sliding piston is provided in the cylinder portion of the master cylinder. Mounted to front and rear ends of the piston are rubber piston cups for sealing a gap between the piston and the cylinder.
However, in simply fitting the rubber piston cup in the gap, a smooth operation is hard to expect because a sliding resistance is made too high. Thus, it has thus far been considered that the sliding resistance is lowered by coating a fluorine resin on the surface of the rubber substrate or by applying a fluorine plasma treatment.
Second Prior Art
Conventionally, a fuel cap is provided on a front end of a fuel pipe, that is, on an opening portion thereof for feeding a fuel such as gasoline. The fuel cap is provided with a closing sealing member for allowing the exterior and interior of the pipe to communicate to each other to discharge the gas in the pipe to the outside when a gas pressure in the fuel pipe exceeds a predetermined value. The closing sealing member is generally formed of rubber to be plate-shaped, and the biasing force of a coil spring causes the closing sealing member to constantly abut against a tubular section disposed on the pipe side so as to close a front end of the pipe. When the gas pressure in the fuel pipe exceeds the biasing force of the coil spring, the closing sealing member is separated from the above tubular section under the action of the pressure, thereby allowing the interior and the exterior of the pipe to communicate to each other. Thus, an abnormal rise in gas pressure in the pipe is suppressed.
Since there is hardly any opportunity of the closing sealing member being open, however, the closing sealing member may happen to closely adhere to the tubular section over a long-term use. In such cases, there was a fear that the closing sealing member will not open even if the gas pressure in the pipe exceeds a predetermined value. For this reason, conventionally, molybdenum disulfide (powdery substance) or the like has been applied to a surface of the closing sealing member which abuts against the tubular section in order to suppress such close adherence.
Third Prior Art
Conventionally, a capability of preventing the gas outflow of gasoline or the like (gas barrier capability) and capability of preventing the fluid outflow has been required of rubber products such as fuel hoses. For this purpose, a fluorine resin tube may be provided on the inner peripheral surface of a hose.
However, in the first prior art, while the sliding resistance can be reduced by coating a fluorine resin on the surface of a rubber substrate or by applying a fluorine plasma treatment, either case has been insufficient in wear resistance. Not to say lack of cohesive force in coating film or plasma treated film, this is believed to be attributable to lack of connecting force or adhesive force between these films and the rubber substrate.
Thus, peeling of the film from the substrate resulted in disadvantages that the sliding resistance increases and abnormal sounds accompanied by sliding generate, thereby reducing practicability.
In the second prior art described above, molybdenum disulfide or the like adhering to a surface of the closing sealing member, which abuts against the tubular section, for the suppression of close adherence is simply rubbed onto such surface, and so is deficient in durability. More specifically, molybdenum disulfide or the like is problematic in such close adherence since it falls off the closing sealing member over a long-term use. Especially, in the case where molybdenum disulfide or the like falls off, forces caused by close adherence are made large in the presence of plasticizer in rubber or impurities in gasoline, so that there is a fear of the sealing member being not open when necessary.
Furthermore, in the third prior art described above, the treatment is applicable to nearly straight fuel hoses or the like, but inapplicable to a complicated-shaped member having many curved portions or a member such as diaphragms and constant-velocity joint boots, which are forced to frequently deform. This is because a fluorine resin tube is poor in shape followability and relatively small in adhesion to the substrate. Thus, in the present circumstances, no such product satisfying the gas barrier capability or liquid outflow preventing capability has been obtained.